The transport of data over error prone links could lead to corruption and/or occasional loss of data unless re-transmission of data received in error or data that is not received at all is carried out. Since for real-time data, such re-transmissions hinder the timely delivery of data, usually data with real-time requirements is delivered with errors and/or sometimes with gaps (data loss) to the real-time application. Most real-time applications can tolerate the gaps in data as long as it has not lost some synchronization points (such as message boundaries). Upon synchronization losses, real-time applications need a reliable mechanism to get back into synchronization. This mechanism should also work for a bi-directional data transport schemes that do not or cannot allow for re-transmissions of data. Moreover, the real-time applications can exchange variable sized messages made up of variable sized data frames or they could interleave fixed size messages with variable sized ones, which makes the detection of synchronization losses more challenging than the case where applications exchange fixed size messages or fixed size data frames or both.
In the Mobile Industry Processor Interface (MIPI) Alliance, several hardware interface standards are being developed so as to enable the seamless interfacing between processors and other application specific integrated circuits (ASICs) in a mobile platform. Unified Protocol (UniPro), which is one such hardware interface standard, enables data exchange at high speeds between different components on a mobile system over chip-to-chip networks built up of high speed serial links. It is a generic, strongly layered protocol based on ISO-OSI reference protocol stack that provides error handling (through re-transmissions based on Cyclic Redundancy Checks (CRC)), flow control, routing and Quality of Service (QOS) guarantees. Some of the applications supported by UniPro belong to the real-time category. Real-time applications generate data streams which require timely delivery. In other words, if the data is not delivered before a particular deadline, it is of no use. An example of such an application is raw video where data is uncompressed and bandwidth requirement is around 500 Mbps. For such applications, error handling through re-transmissions hinders timely delivery.
Hence it is better to deliver data with errors. Most of the time, the receivers can tolerate loss of data but losing synchronization information can be a problem. For example, there are generally two types of synchronization signals in video: horizontal sync, and vertical sync. In a very simplified manner, horizontal sync signals tell the processor when to move the video signal to the next lower line across the screen and the vertical sync signal tells the processor when to start again from the top of the screen. Loss of either or both of these signals could severely affect the quality of the displayed video.
Therefore, there is a need for a protocol to detect loss of synchronization information at the receiver and communicate it to the transmitter. An additional requirement for this protocol is that it should be simple (i.e., be easily integrated to existing or emerging data transport protocols such as UniPro) and also it should not rely upon any reliable mode of communication. Accordingly, it would be desirable to provide methods, modes and systems for detection and communication of synchronization loss and synchronization regain in a real time data transfer scheme that is easily integrated and is reliable.